Secondary physical random access channel (PRACH) configuration for contention based random access in new radio systems

Abstract

A device of a New Radio (NR) evolved Node B (gNodeB), a method and a machine readable medium to implement the method. The method includes: processing a first signal sent by a NR evolved NodeB (gNodeB) regarding a primary physical random access channel (PRACH) configuration to be used to encode for transmission a first communication to the gNodeB; processing a second signal sent by the gNodeB regarding a secondary PRACH configuration different from the primary PRACH configuration and to be used to encode for transmission a second communication to the gNodeB; determining the primary PRACH configuration from the first signal and the secondary PRACH from the second signal; and switching from the primary PRACH configuration to the secondary PRACH configuration and encode for transmission the second communication to the gNodeB based on the secondary PRACH configuration.

What is claimed is: 
     
       1. A user equipment (UE), comprising:
 a Radio Frequency (RF) interface, and 
 a baseband processor configured to:
 receive information from a base station indicating a first physical random access channel (PRACH) configuration and a second PRACH configuration different from the first PRACH configuration; 
 transmit, via the RF interface, a first communication based on the first PRACH configuration; and 
 in response to satisfaction of a triggering condition or explicit signaling from the base station, switch from the first PRACH configuration to the second PRACH configuration; and 
 transmit, via the RF interface, a second communication based on the second PRACH configuration. 
 
 
     
     
       2. The UE of  claim 1 , wherein the base station is an integrated access and backhaul (IAB) parent node, and wherein the UE is one of a NR UE or an IAB child node. 
     
     
       3. The UE of  claim 1 , wherein the information is received from the base station in one of a radio resource control (RRC) signal, a system information (SI) signal, or a group-common physical downlink control channel (GC-PDCCH) signal. 
     
     
       4. The UE of  claim 1 , wherein the first PRACH configuration and the second PRACH configuration are both contention-based PRACH configurations. 
     
     
       5. The UE of  claim 1 , wherein the triggering condition includes a predetermined number of failed transmission attempts of the first communication to the base station using the first PRACH configuration. 
     
     
       6. The UE of  claim 1 , wherein the explicit signaling is part of one of:
 a system information (SI) radio resource control (RRC) message from the base station; 
 a group-common physical downlink control channel (PDCCH) including a downlink control information (DCI) format 2_4; 
 a user equipment-specific (UE-specific) RRC message including a downlink downlink control channel message (DL-DCCH-message); 
 a medium access control control channel (MAC CE); or 
 a UE-specific DCI format. 
 
     
     
       7. The UE of  claim 6 , wherein:
 the explicit signaling is part of the SI RRC message, the SI RRC message includes an cell-specific indication of a selection as between the first PRACH configuration and the second PRACH configuration; 
 the explicit signaling is part of the DCI format 2_4, the DCI format 2_4 includes an indication of a selection as between the first PRACH configuration and the second PRACH configuration that is for one user equipment (UE), or for a group of UEs from one or multiple serving cells; 
 the explicit signaling is part of the DL-DCCH-message, the DL-DCCH message includes a RRC information element (IE) to indicate a cell-specific selection as between the first PRACH configuration and the second PRACH configuration; 
 the explicit signaling is part of the MAC CE, the MAC CE includes a 1-bit field to indicate a selection as between the first PRACH configuration and the second PRACH configuration; or 
 the explicit signaling is part of the UE-specific DCI format, the UE-specific DCI format includes a selection as between the first PRACH configuration and the second PRACH configuration for multiple serving cells. 
 
     
     
       8. The UE of  claim 7 , wherein the explicit signaling is part of the DCI format 2_4, and the baseband processor is configured to decode a cyclic redundancy check (CRC) based on a secondary random access (SRA) radio network temporary identifier (RNTI) (SRA-RNTI). 
     
     
       9. The UE of  claim 1 , wherein the information includes information regarding a triggering condition to trigger a switch between the first PRACH configuration and the second PRACH configuration, and the baseband processor is configured to switch based on the triggering condition. 
     
     
       10. The UE of  claim 1 , wherein the baseband processor is configured to use the second PRACH configuration to encode uplink (UL) slots within a semi-static downlink/uplink (DL/UL) period to avoid interference from remote cells. 
     
     
       11. A method, comprising:
 receiving information from a base station indicating a first physical random access channel (PRACH) configuration and; 
 a second PRACH configuration different from the first PRACH configuration; 
 transmitting a first communication based on the first PRACH configuration; 
 in response to satisfaction of a triggering condition or explicit signaling from the base station switching from the first PRACH configuration to the second PRACH configuration; and 
 transmitting a second communication based on the second PRACH configuration. 
 
     
     
       12. The method of  claim 11 , wherein first PRACH configuration and the second PRACH configuration are both contention-based PRACH configurations. 
     
     
       13. The method of  claim 12 , wherein the triggering condition includes a predetermined number of failed transmission attempts of the first communication to the base station have taken place using the first PRACH configuration. 
     
     
       14. The method of  claim 12 , wherein the explicit signaling is part of one of:
 a system information (SI) radio resource control (RRC) message from the base station; 
 a group-common physical downlink control channel (PDCCH) including a downlink control information (DCI) format 2_4; 
 a user equipment-specific (UE-specific) RRC message including a downlink downlink control channel message (DL-DCCH-message); 
 a medium access control control channel (MAC CE); or 
 a UE-specific DCI format. 
 
     
     
       15. The method of  claim 14 , wherein:
 where the explicit signaling is part of the SI RRC message, the SI RRC message includes an cell-specific indication of a selection as between the first PRACH configuration and the second PRACH configuration; 
 where the explicit signaling is part of the DCI format 2_4, the DCI format 2_4 includes an indication of a selection as between the first PRACH configuration and the second PRACH configuration that is for one user equipment (UE), or for a group of UEs from one or multiple serving cells; 
 where the explicit signaling is part of the DL-DCCH-message, the DL-DCCH message includes a RRC information element (IE) to indicate a cell-specific selection as between the first PRACH configuration and the second PRACH configuration; 
 where the explicit signaling is part of the MAC CE, the MAC CE includes a 1-bit field to indicate a selection as between the first PRACH configuration and the second PRACH configuration; or 
 where the explicit signaling is part of the UE-specific DCI format, the UE-specific DCI format includes a selection as between the first PRACH configuration and the second PRACH configuration for multiple serving cells. 
 
     
     
       16. The method of  claim 15 , further including, where the explicit signaling is part of the DCI format 2_4, decoding a cyclic redundancy check (CRC) based on a secondary random access (SRA) radio network temporary identifier (RNTI) (SRA-RNTI). 
     
     
       17. The method of  claim 16 , further including determining the SRA-RNTI from higher layer signaling by the base station. 
     
     
       18. A baseband processor configured to perform operations, the operations comprising
 receiving information from a base station indicating a first physical random access channel (PRACH) configuration and; 
 a second PRACH configuration different from the first PRACH configuration; 
 instructing a transceiver to transmit a first communication based on the first PRACH configuration; 
 in response to satisfaction of a triggering condition or explicit signaling from the base station switching from the first PRACH configuration to the second PRACH configuration; and 
 instructing the transceiver to transmit a second communication based on the second PRACH configuration. 
 
     
     
       19. The baseband processor of  claim 18 , wherein the base station is an integrated access and backhaul (IAB) parent node, and wherein the baseband processor is associated with one of a NR User Equipment (UE) or an IAB child node. 
     
     
       20. The baseband processor of  claim 18 , wherein the triggering condition includes a predetermined number of failed transmission attempts of the first communication to the base station using the first PRACH configuration. 
     
     
       21. The baseband processor of  claim 18 , wherein the first PRACH configuration and the second PRACH configuration are both contention-based PRACH configurations.